Cross-kingdom RNA communication during smut fungal infection by Thecaphora thlaspeos

• Applicant: Professorin Dr. Vera Göhre
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems ; Plant Breeding and Plant Pathology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462242123

During infections, pathogens communicate with their host to supress the plant immune system and modify plant metabolism. While in the classical view, protein effectors are the main player, recently it has become apparent that also RNAs are exchanged and contribute to cross-kingdom communication. A proposed delivery mechanism is the transport in extracellular vesicles (EVs) that translocate from the pathogen to the host cell to deliver their cargo. The genetically tractable smut fungi are ideal systems to study EV-mediated cross-kingdom RNA communication. Pioneering work on mRNA transport in EVs is carried out in the model smut fungus Ustilago maydis. In this proposal, we focus on cross-kingdom RNA communication in the Brassicaceae smut fungus T. thlaspeos, which we have recently established as a genetically tractable pathogen of the model plant Arabidopsis thaliana. We will first provide an inventory of the EV cargo to subsequently address the functional relevance of cross-kingdom RNAi and EV-mediated mRNA transport for virulence. In contrast to U. maydis, T. thlaspeos has retained the RNAi machinery, so that in a comparative approach, we will determine the relative contribution of mRNA and sRNA translocation to infection. What is the core cargo of EVs? Do mRNAs and sRNA target the same plant processes? In the frame of the RU5116, exRNA communication, T. thlaspeos will present the smut fungal pathogens, since it is able to use both sRNAs and mRNAs for cross-kingdom communication. We will compare RNA effectors in particular to vascular root pathogens, mutualists and pathogens during perennial infections. Thereby, we will gain detailed insight into the functional role of RNA effectors in plant-microbe interactions. In the future, elucidation of the molecular mechanisms of EV loading will be important to understand how RNAs are targeted for translocation vs. translation in the pathogen.

• DFG Programme: Research Grants